Adding x-ray mode

[briandk]

@alloy-d suggests:

You'd add an "x-ray" class to an ancestor of the commits via JS, then use !important to override font colors within that element.

So,

1. define a separate xray.css stylesheet
2. in xray.css, create a selector for, say, .xray that defines a look for font-color
3. Also define a separate selector for elements that are a line-highlight class

[briandk]

Adding and removing classes to elements can be accomplished with jquery

$("p").addClass("myClass yourClass"); // adds myClass and yourClass to all <p> elements
$('p').removeClass('myClass yourClass') // removes myClass and yourClass from all <p> elements

[briandk]

Also: we need to modify the Python logic to write out line-highlight strings. This should probably be handled in the view class.

[briandk]

We may want to change how we do this. As @alloy-d and I discussed, what we might think about is:

• Computing the lines that haven't changed in Python (it's the complement of the list of lines that have changed)
• (optional) munging the unchanged lines list to break it into longer contiguous spans
• hacking a version of lea verou's line highlight plugin to draw divs that mask the unchanged code